Abstract: This paper describes the development of the O'Hare Airport Transit System, as well as, the individual subsystem elements which make up the entire system. In addition, the paper also describes the extensive test program which was used to qualify, in some cases, and verify that the system met the minimum contract requirements. The topics covered in this paper are as follows: a) Planning and implementation. b) Structure design and facility design. c) Trackwork. d) Passenger cars. e) Power distribution. f) Maintenance building. g) Testing. h) Stations.